Large buildings such as schools, wholesale and retail establishments, manufacturing plants, etc. are often fabricated utilizing steel joists. The joists are extended between the walls of the building, or between girders which extend between the walls, and support either a higher floor of the building or the building roof. Typically, the joists are in turn interconnected by transversely extending rods or angle irons in a procedure known as "bridging".
Heretofore, bridging systems for steel joists have required the use of welding. In accordance with the usual procedure, the steel joists are positioned in the building and the transversely extending rods or angle irons are then secured to each joist by means of welding. This procedure is unsatisfactory for at least two reasons. First, expensive welding equipment must be maintained at the job site throughout the construction process, thereby increasing construction costs. Second, welding operations must be performed by skilled, highly paid laborers, thereby further increasing construction costs.
Another problem which is inherent in the practice of present bridging procedures involves the fact that in many instances the design of the building requires the precise positioning of the bridging members relative to the joists. When the bridging members are installed in the field, it is impossible from any practical standpoint to insure that the bridging members will be properly placed. Problems of this nature are frequently encountered when the design of the bridging system involves the positioning of bridging members at unequal intervals.
The present invention comprises a bridging system for steel joists which overcomes the foregoing and other problems long since associated with the prior art. In accordance with the broader aspects of the invention, fasteners are secured to the joists at the time of manufacture. This is highly advantageous in that the location of the component parts of the bridging system is under the control of the joist manufacturer, rather than construction personnel.
After the joists are installed, preformed bridging members are extended between adjacent joists and are secured thereto. The bridging members are secured to the fasteners and therefore to the joists mechanically, rather than by welding. This is higly advantageous in that it eliminates both the necessity of providing welding equipment at the job site and the necessity of utilizing skilled labor to construct the bridging system.
In accordance with more specific aspects of the invention, the bridging members are preferably perforated at spaced apart intervals, and are therefore adapted for universal application regardless of joist spacing. The bridging members may be provided with additional sets of perforations to facilitate the installation of bracing members therebetween. The fasteners that are secured to the joists may be threaded, in which case nuts are used to secure the bridging members in place. Alternatively, the fasteners may comprise steel dowels, in which case retaining rings are used to secure the bridging members in place.